What are the reasons for a car not accelerating when the throttle is fully pressed?
3 Answers
Reasons for a car not accelerating when the throttle is fully pressed: 1. A dirty throttle position sensor or voltage imbalance can cause electronic throttle failure; 2. Air intake system leakage or blockage; 3. The use of poor-quality gasoline may lead to fuel pump burnout, catalytic converter failure, piston failure, etc., directly affecting engine power. Modern cars use an electronic throttle system. When the driver presses the accelerator pedal, the accelerator pedal position sensor generates corresponding voltage signals that are input into the throttle control unit. After processing the signals, the control unit calculates the basic torque demand of the engine and determines the corresponding basic desired throttle angle. If a sensor sends an incorrect signal during this process, the control unit may misjudge the car's operating conditions, resulting in the inability to accelerate despite pressing the throttle.
That day when I took my old Focus on the highway, I encountered this issue—no matter how hard I pressed the gas pedal, the speed wouldn’t go above 80 mph. I figured a few things could be wrong: the fuel pump might not be supplying enough fuel, making it feel like it’s gasping for air; the ignition coils or spark plugs might be worn out, causing incomplete combustion; or the catalytic converter might be clogged, restricting exhaust flow like trying to run with a pinched nose. For an automatic transmission, you also need to check the gearbox—if the clutch plates are slipping or the torque converter is faulty, it’s like climbing a mountain in slippers. Last time my car had this problem, it was the mass airflow sensor that failed, causing the ECU to miscalculate the fuel mixture. Replacing the sensor cost me 300 bucks and fixed it. Ignoring these issues can seriously damage the engine, so it’s best to head to a repair shop and scan for trouble codes ASAP.
Having driven for over 20 years, what I fear most is throttle failure. When pressing the accelerator yields no response, it's usually due to one of these issues. First, listen to the engine sound. If the RPM increases but the vehicle speed doesn't, it's likely a problem with the clutch or transmission. If the RPM doesn't rise at all, focus on checking the fuel system and electrical circuits. Older cars often suffer from clogged fuel filters causing insufficient fuel supply, while newer models might have sticky electronic throttle bodies. Once, while helping a neighbor inspect their car, I found the fuel tank's suction pipe screen clogged with debris, preventing the fuel pump from drawing fuel. Additionally, a faulty brake light switch can make the car think it's braking, causing the computer to limit speed. For such faults, it's best not to tinker yourself; having a mechanic check with a diagnostic tool is the most hassle-free solution.
